Anticholinesterases

Acetylcholinesterase inhibitor

Reversibly inhibits AChE → ↑ACh at NMJ → outcompetes non-depolarizing relaxants. Co-administer antimuscarinic (glycopyrrolate or atropine) to block muscarinic side effects.

Quaternary acetylcholinesterase inhibitor

Reversibly inhibits acetylcholinesterase → ↑acetylcholine at the neuromuscular junction. Quaternary ammonium → does NOT cross BBB → no CNS effects. Longer-acting than neostigmine; mainstay of chronic myasthenia gravis treatment.

Short-acting acetylcholinesterase inhibitor

Reversible AChE inhibitor with the FASTEST onset (1–2 min) and SHORTEST duration (5–10 min) of the anticholinesterases. Quaternary structure → no CNS penetration. Largely historical; replaced by sugammadex in NMB reversal and by serologic AChR antibody testing in myasthenia diagnosis.

Tertiary-amine acetylcholinesterase inhibitor (CNS-active)

Reversible AChE inhibitor with TERTIARY amine structure → CROSSES blood-brain barrier (unlike neostigmine, pyridostigmine, edrophonium). The only AChE inhibitor that treats CENTRAL anticholinergic syndrome.